William and Kate, the Duke and Duchess of Cambridge, flanked by Governor General David Johnston, left, and Immigration Minister Jason Kenney smile during a group photo with newly sworn-in Canadians at a citizenship ceremony Friday, July 1, 2011 in Gatineau, Canada.

Credit: AP PhotoThe Canadian Press, Paul Chiasson

William and Kate, the Duke and Duchess of Cambridge, share a laugh after signing a guest book at a citizenship ceremony Friday, July 1, 2011, in Gatineau, Canada.

Prince William greets a new Canadian citizen during citizenship ceremony Friday, July 1, 2011, in Gatineau, Canada. The Duke and Duchess of Cambridge watched new citizens take the oath of citizenship, in which new Canadians pledge allegiance to the Queen, who is William's grandmother.

William and Kate, the Duke and Duchess of Cambridge, flanked by Sharon Johnston, wife of Governor General David Johnston and Immigration Minister Jason Kenney, listen to proceedings during a citizenship ceremony on Friday, July 1, 2011, in Gatineau, Canada.

Kate, Duchess of Cambridge, smiles as she take part in a citizenship ceremony at the Museum of Civilization in Gatineau, Canada, on Friday, July 1, 2011. The duchess was dressed in Canadian colors - a cream dress by the London designer Reiss, complete with the Queen's Maple Leaf brooch, and a red hat topped with a maple leaf. Queen Elizabeth II loaned the brooch to the duchess for the tour; it was first worn in 1951 by the then-Princess Elizabeth on her first visit to Canada.

Prince William's wife, Catherine, Duchess of Cambridge, waves to the crowd as she arrives at the Museum of Civilization with Sharon Johnston, wife of the Governor General of Canada, in Gatineau, Quebec, Canada, July 1, 2011.

William and Kate, the Duke and Duchess of Cambridge, arrive at a citizenship ceremony in Gatineau, Quebec, Canada, on July 1, 2011. The royal couple watched new citizens take the oath of citizenship, in which new Canadians pledge allegiance to the Queen, who is William's grandmother.